- Be angry and do not sin. Not all anger is sin, as evidenced by Jesus' righteous fury with those making a mockery of the temple, as well as the times when God's anger was kindled in the Old Testament. So there is a justified precedent for being angry, but we must make sure that when we are angry that we do not sin. Because anger is an emotion, it must be tamed and admonished and treated carefully. Often, anger leads to impatience (and patience is a part of the fruit of the Spirit) and a harsh tongue. These things must be avoided.
- Do not let the sun go down on your anger. For some, this means reconcile your differences literally before the sun goes down. While this can be good, it can also create problems. For me, it's more metaphor. Problems and enmity between people should be resolved, and in an acceptable time frame, but I'm of the opinion of letting things set for a while to let the anger die down. This allows one to pray and collect one's thoughts so as not to say or do anything rash. Whatever your opinion is on this, whether literal or not, Paul makes it clear that you cannot allow anger to stay pent up and unresolved. This is especially true among church members, as it can fester and tear apart the body.
I find this verse interesting. No doubt we all get angry, but it's how we react to that anger that's important.